Recently, due to problems of environmental pollution and fossil energy depletion in the earth, the development of eco-friendly alternative energy sources and the diversification of future energy sources have appeared as international issues. Under the circumstances, a solar cell has been spotlighted as a future influential alternative energy source, and a continuous drop in the price of the solar cell has caused a world market size related to the solar cell to be rapidly increased.
A solar cell module, which is an essential element in a solar photovoltaic power generation system, has advantages in that a lifetime of about 20 years or more so that it may be semi-permanently used, and a large-sized solar cell module as well as a small-sized solar cell module can be freely manufactured depending on installation locations and scales. In a solar cell module, a thermal bonding process by which solar cells are modularized by being connected to one another in series via power lines, i.e., metal electrodes (ribbons), is referred to as a tabbing or soldering process. A conventional tabbing process is performed in such a manner that a bonding portion between a metal electrode (or ribbon) and a solar cell is heated using a halogen infrared lamp (IR tabbing process) or manually welded by a worker. However, the aforementioned methods, particularly, the IR tabbing process has a problem in that a zone directly irradiated by the infrared lamp is excessively larger than a bonding area required for the tabbing process so that a solar cell module may be more likely to be damaged during the tabbing process. Typically, a solar cell such as a crystal silicon solar cell has a multi-layered structure (e.g., including Al coating layer, Si wafer layer and SiN3Ar coating layer) of which the layers are made of different materials. Accordingly, if a directly-irradiated zone is excessively large as described above in the same manner as the conventional IR tabbing process, differences in thermal expansion/contraction behaviors of the materials for the respective layers of the solar cell upon application of thermal energy thereto cause the solar cell module to be bent up to 3 mm, resulting in defects in the solar cell module, such as a crack, breakage, damage or warping.
These problems hinder the recently required thinness of solar cells. That is, most of the crystal silicon solar cells, which have been conventionally used, generally have a thickness of about 230 μm, but solar cells even having a thickness of about 50 μm have the substantially same efficiency. Accordingly, since the silicon depletion and the increasing manufacturing cost caused by the increasing demand for silicon have been recently raised, recently, the requirements for thinness of solar cells are increased. As such, the problems of the conventional tabbing process would be more raised, and therefore, a new tabbing method has been required in which a direct radiation zone in a solar cell is minimized during the tabbing process, thereby preventing the solar cell from being damaged due to different physical properties (thermal expansion/contraction coefficient, and the like) of materials of a multi-layered structure, the bonding property and boding uniformity between the solar cell and electrodes can be improved, and the manufacturing efficiency can be increased.